The use of 3,3'dichlorobenzidine in certain industrial processes poses a potential occupational and environmental health hazard due to potent carcinogenicity of this chemical in animal species. Recent studies suggest that dichlorobenzidine, unlike most carcinogenic aromatic amines, is biologically active without prior metabolism. At present, little information exists on the fate of dichlorobenzidine in mammals, and nothing is known about the mechanistic basis for its biological action. Current evidence suggests a long retention of the chemical in the body and a low degree of metabolism. This, coupled with the ability to act directly on biological systems, may serve to enhance the carcinogenic properties of dichlorobenzidine in humans. This study proposes to obtain detailed information on the distribution and metabolism of dichlorobenzidine in mammals, and to investigate the potential for its interactions with functionally important biological macromolecules as the basis for its mutagenic and carcinogenic properties. The absorption, distribution, excretion, and metabolism of dichlorobenzidine will be examined in the rat in vivo, and the effect of sex, species, and enzyme induction assessed. The metabolism of the chemical will be studied in vitro and the mutagenicity of metabolites will be assessed. The ability of dichlorobenzidine and/or its metabolites to interact directly with biological macromolecules will be examined as the potential basis for its carcinogenic action.